The present invention relates generally to a method of making combustion chamber liners and more particularly to a method which improves the strength and durability of the liners.
Flowpath gases in gas turbine engines are mixed with fuel and burned to heat the gases. The mixing and burning occurs in an annular combustion chamber formed between an annular inner liner and an annular outer liner. A dome at the upstream end of the combustion chamber includes fuel nozzles which deliver fuel to the chamber and mix the fuel with the flowpath gases. This mixture is ignited and burned to heat the flowpath gases. The flowpath gases are not uniformly heated resulting in large thermal gradients around the inner and outer liners which produce large differences in stresses around the liners.
Most conventional liners are fabricated from sheet metal or forged rings. Sheet metal liners are made by brazing sheet metal rings together, and forged liners are made by welding forged rings together. Both types of rings usually have axial seams. Although some of these seams have reduced material properties and cause stress concentrations, no provision has been made heretofore to position the seams in areas of the liner having lower stresses. Thus, the strength and durability of conventional liners is generally limited by the reduced material properties found in the seams.
Among the several features of the present invention may be noted the provision of a method of fabricating an annular liner for a combustion chamber of a gas turbine engine. The combustion chamber has a dome including a fuel nozzle for delivering fuel to the combustion chamber. A metal piece is formed into an annular section constituting at least a portion of the liner and having at least one seam extending generally axially with respect to an axial centerline of the liner. An upstream end of the liner is machined to have a registration feature for connecting the liner to the combustion chamber dome in at least one predetermined orientation with respect to the dome. Further, the method includes ensuring the registration feature and the seam are located relative to each other on the liner so the seam is at a preselected position with respect to the combustion chamber dome when the liner is connected to the combustion chamber dome in the predetermined orientation.
In another aspect the method of the present invention includes the steps of forming a first metal piece into a first annular section having at least one welded seam extending generally axially with respect to an axial centerline of the liner and forming a second metal piece into a second annular section. The first and second annular sections are joined. An end of the second annular section is machined after the first and second annular sections are joined to have a registration feature for connecting the liner to the combustion chamber dome in at least one predetermined orientation. The registration feature is located relative to the seam so the seam is at a preselected position with respect to the combustion chamber dome when the liner is connected to the combustion chamber dome in the predetermined orientation.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.